Underwater imaging system

ABSTRACT

A method and apparatus provides for improved imaging of objects underwater. The method and apparatus are particularly useful in a degraded underwater visual environment. The method and apparatus are also useful in undersea operations in which enhanced visualization at close range is desirable. Exemplary operations include diver assist, ship hull inspections, underwater robotic operations (e.g. sample collection, mine neutralization), etc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application ofPCT/US2019/045701, filed Aug. 8, 2019, which claims priority toApplication Ser. No. 62/742,620 filed on Oct. 8, 2018 entitledUNDERWATER IMAGING SYSTEM, the contents of which applications areincorporated herein by reference in their entireties for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention(s) was made with government support under contract numberN0025317C0028 awarded by the Naval Undersea Warfare Center. Thegovernment has certain rights in the invention(s).

FIELD OF DISCLOSURE

This disclosure relates generally to systems and methods for underwaterimaging, and more particularly, to imaging of objects underwater in anunderwater visual environment where enhanced visualization is desirable.

BACKGROUND

In turbid or turbulent mediums, such as underwater environments, anillumination pattern may be degraded when propagating from anilluminator to a target. Degradation can be caused by multiple factors.Exemplary factors include contrast loss from common volumes scattering,blurring such as from forward scattering/beam wandering, and exponentialattenuation of target returns.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of one or more embodiments or examples ofthe present teachings. This summary is not an extensive overview, nor isit intended to identify key or critical elements of the presentteachings, nor to delineate the scope of the disclosure. Rather, itsprimary purpose is merely to present one or more concepts in simplifiedform as a prelude to the detailed description presented later.Additional goals and advantages will become more evident in thedescription of the figures, the detailed description of the disclosure,and the claims.

The foregoing and/or other aspects and utilities embodied in the presentdisclosure may be achieved by providing a system and method for imagingunderwater objects, including generating spatially varying modulation ona beam of light using a spatial light modulator, illuminating a targetwith the beam of light having spatially varying modulation, capturing animage of said target illuminated with said light having said spatiallyvarying modulation using a dynamic range detector, and post processingthe captured image.

According to aspects described herein, an apparatus for imagingunderwater objects includes a spatial light modulator, a light source,and a dynamic range detector. The spatial light modulator generatesspatially varying modulation on a beam of light. Thea light sourceilluminates a target with the modulated beam of light having spatiallyvarying modulation to produce a sequence of coded illumination patternsprojected on the target. The dynamic range detector captures a pluralityof images of the target illuminated with the modulated beam of lighthaving the sequence of coded illumination patterns. The apparatus mayalso include a controller configured to receive digital modulationpattern data and modify the spatial light modulator to modulate the beamof light in accordance with the received digital modulation patterndata, and a computer providing post processing of the captured images.

According to aspects illustrated herein, a method for imaging underwaterobjects includes emitting a beam of light from a light source,generating spatially varying modulation on the beam of light using aspatial light modulator, modifying the spatial light modulator with acontroller to modulate the beam of light in accordance with receiveddigital modulation pattern data, illuminating a target with themodulated beam of light having spatially varying modulation to produce asequence of coded illumination patterns, capturing a plurality of imagesof the target illuminated with the modulated beam of light having thesequence of coded illumination patterns, with at least two of theplurality of images corresponding to different ones of the codedillumination patterns using a dynamic range detector, and postprocessing the captured images.

Exemplary embodiments are described herein. It is envisioned, however,that any system that incorporates features of apparatus and systemsdescribed herein are encompassed by the scope and spirit of theexemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the disclosed apparatuses, mechanismsand methods will be described, in detail, with reference to thefollowing drawings, in which like referenced numerals designate similaror identical elements, and:

FIG. 1 a block diagram of an apparatus for imaging objects underwater inaccordance with examples of the embodiments;

FIG. 2 is a side view of an optical engine in accordance with examplesof the embodiments;

FIG. 3 illustrates an exemplary modulation pattern of light that isilluminating a target;

FIG. 4 illustrates an exemplary post processing of exemplary capturedimages;

FIG. 5 is a flowchart depicting the operation of an exemplary method forimaging underwater objects;

FIG. 6A is a front view of an optical engine having exemplary dimensionsaccording to examples;

FIG. 6B a front view of a detector (e.g., camera) having exemplarydimensions according to examples;

FIG. 7 is a table showing cumulative AZ dust, C and beam attenuationlengths for images taken of underwater target at a distance of 4.3meters;

FIG. 8A is an image of underwater target taken with a Thorlabs DCC3626camera and floor illumination;

FIG. 8B is an image of underwater target taken with a Nikon camera andflood illumination;

FIG. 9A is an image of underwater target taken with a Thorlabs DCC3626camera and floor illumination;

FIG. 9B is an image of underwater target taken with a Nikon camera andflood illumination;

FIG. 9C is a post processed image of underwater target taken with aThorlabs DCC3626 camera with coded illumination and post processing viaan example of the embodiments;

FIG. 10A is an image of underwater target taken with a Thorlabs DCC3626camera and floor illumination;

FIG. 10B is an image of underwater target taken with a Nikon camera andflood illumination;

FIG. 10C is a post processed image of underwater target taken with aThorlabs DCC3626 camera with coded illumination and post processing viaan example of the embodiments;

FIG. 11A is an image of underwater target taken with a Thorlabs DCC3626camera and floor illumination;

FIG. 11B is an image of underwater target taken with a Nikon camera andfloodlight illumination; and

FIG. 11C is a post processed image of underwater target taken with aThorlabs DCC3626 camera with coded illumination and post processing viaan example of the embodiments.

DETAILED DESCRIPTION

Illustrative examples of the devices, systems, and methods disclosedherein are provided below. An embodiment of the devices, systems, andmethods may include any one or more, and any combination of, theexamples described below. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth below. Rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Accordingly, the exemplary embodiments are intended to cover allalternatives, modifications, and equivalents as may be included withinthe spirit and scope of the apparatuses, mechanisms and methods asdescribed herein.

We initially point out that description of well-known startingmaterials, processing techniques, components, equipment and otherwell-known details may merely be summarized or are omitted so as not tounnecessarily obscure the details of the present disclosure. Thus, wheredetails are otherwise well known, we leave it to the application of thepresent disclosure to suggest or dictate choices relating to thosedetails. The drawings depict various examples related to embodiments ofillustrative methods, apparatus, and systems for printing onto asubstrate web and automatically stacking individual sheets of the webfor AM manufacturing.

When referring to any numerical range of values herein, such ranges areunderstood to include each and every number and/or fraction between thestated range minimum and maximum. For example, a range of 0.5-6% wouldexpressly include the endpoints 0.5% and 6%, plus all intermediatevalues of 0.6%, 0.7%, and 0.9%, all the way up to and including 5.95%,5.97%, and 5.99%. The same applies to each other numerical propertyand/or elemental range set forth herein, unless the context clearlydictates otherwise.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (forexample, it includes at least the degree of error associated with themeasurement of the particular quantity). When used with a specificvalue, it should also be considered as disclosing that value. Forexample, the term “about 2” also discloses the value “2” and the range“from about 2 to about 4” also discloses the range “from 2 to 4.”

The term “controller” is used herein generally to describe variousapparatus relating to the operation of one or more device that directsor regulates a process or machine, including a spatial light modulator(SLM). A controller can be implemented in numerous ways (e.g., such aswith dedicated hardware) to perform various functions discussed herein.A “processor” is one example of a controller which employs one or moremicroprocessors that may be programmed using software (e.g., microcode)to perform various functions discussed herein. A controller may beimplemented with or without employing a processor, and also may beimplemented as a combination of dedicated hardware to perform somefunctions and a processor (e.g., one or more programmed microprocessorsand associated circuitry) to perform other functions. Examples ofcontroller components that may be employed in various embodiments of thepresent disclosure include, but are not limited to, conventionalmicroprocessors, application specific integrated circuits (ASICs), andfield-programmable gate arrays (FPGAs).

FIG. 1 illustrates a block diagram of an apparatus 10 for imagingobjects underwater in accordance with various exemplary embodiments ofthe present invention. Generally speaking, an underwater target 40 isilluminated and a detector 24 captures an image of target 40. In aturbid/turbulence medium, however, an illumination pattern will bedegraded when propagating from the illuminator to the target. In such aturbid/turbulence medium, a consideration in an active electro-opticalimaging system is to mitigate the contrast loss from common volumesscattering (which is similar to the effect of turning on high-beams infog). Such contrast loss cannot be reduced by averaging multiple frames.

While a detector may be able to capture a relatively large number ofphotons reflecting off of a target, there may be insufficient photons tocapture certain desirable portions of the image. Accordingly, opticalengine 12 may be included. Optical engine 12 may include, for example, aSpatial Light Modulator (SLM) engine 50. Exemplary optical engines mayinclude DLP LightCrafter E4500MKII (available from EKB Technologies).Merely as an example, CEL5500 manufactured by Digital Light Innovationsmay also be used, but is not preferred due to its larger size.

Optical engine 12 includes a SLM engine 50 and light source 16. The SLMengine 50 may include a SLM 14 (e.g., Digital Mirror Device (DMD),liquid crystal SLM, electrically addressed SLM, optically addressedSLM), and a controller 60.

Light source 16 may be a laser source, such as a continuous wave (CW)laser. In one exemplary embodiment of the present invention, lightsource 16 is a laser diode 18 based source, which may include a varietyof light emitters. One example of an integrated laser diode driver andthermoelectric coolers (TEC) module is model LT-LD-TEC-4500 manufacturedby Lasertack. Various wavelength laser diodes may be used based upon theapplication of the present invention. For example, blue laser diodeillumination (approximately 360 nm-480 nm, 446 nm for example) may beused in a seabed imaging system due to its higher optical power output.Green laser (approximately 510 nm-570 nm, 532 nm for example) may bemore preferable than blue laser in shallow coastal water. An LED 20 anda switch 22 are shown in the drawing as an alternative source of lightfor illuminating target 40, but the use of an LED (with or without aswitch) may be optional.

Computer (PC) 30 is also included. Computer 30 has several functions,including power control of light source 16, and providing modulationpattern data to SLM 14. The SLM 14 modulates light received from lightsource 16 based on a modulation pattern data that is provided to SLMengine 50 via computer 30. SLM controller 60 receives the modulationpattern data from computer 30 and modifies the SLM 14 to modulate lightreceived from light source 16 in accordance with the received modulationpattern data from the PC 30. Light thus transmitted towards target 40has a modulation pattern in accordance with the received data.

The apparatus 10 for imaging objects underwater may include detector 24,which captures an image of target 40 that is illuminated by opticalengine 12. In one exemplary embodiment, detector 24 captures photonsreflected off of target 40. In one exemplary embodiment, detector 24 isa camera with high sensitivity and with low noise sensors. Exemplarycameras include Thorlabs DCC3260M, Thorlabs DCC3626DM, and ThorlabsQuantalux. Other cameras that embody CMOS or SCMOS technologies may beused as well. The detector 24 may also be a high dynamic range detector,for example having a high dynamic range of 16 bits or higher.

Data corresponding to the images captured by detector 24 may then betransmitted to computer 30 for further processing. Computer 30 mayperform several steps in order to improve the quality of the imagecaptured by detector 24.

FIG. 2 is a block diagram that illustrates further details of theexemplary optical engine 12 shown in FIG. 1 . The optical engine 12 isshown by example including laser diode 18 that emits light to SLM 14,which modulates the received light according to modulation pattern datareceived from the PC 30. The light may be beam shaped or otherwisemodified between the laser diode 18 and the SLM 14. For example, lightemitted from the laser diode 18 may be homogenized and shaped bymicrolens array 26 and reflected off mirror 28. Mirror 28 may be afolding mirror. The reflected light may be shaped by relay lenses 32 and34, and directed through a prism, such as a Total Internal Reflection(TIR) prism 36. The TIR prism allows the light through to the SLM 14,and reflects the SLM modulated light to projection lens 38 forprojection of the structured light onto the target 40 in codedillumination modulation patterns.

FIG. 3 illustrates an exemplary modulation pattern of light that isilluminating target 40. The modulation pattern of light (or “codebook”)and optionally subsequent patterns can be determined in advance ofactual illumination of the target. The modulation pattern(s) can also berandom (e.g. a Bernoulli random pattern). Using these patterns providesthe ability to record the response of each sub regions in the field ofview under different illumination conditions (i.e., directly illuminatedor not-directly illuminated). In one illumination condition, aparticular subregion may be illuminated, while in another illuminationcondition, that particular subregion may not be illuminated. By analysisof the differences in responses resulting from the use of differentmodulation patterns, the computer 30 is intentionally configured toderive and reduce the interferences from the backscatter.

In one exemplary embodiment, computer 30 removes noise included in theimage captured by detector 200. Noise may be removed by capturingmultiple images of target 40 under different illumination patterns (suchas patterns following Bernoulli random variable distributions, amongothers). In examples, each of the multiple images may be captured undera different illumination pattern. In an exemplary embodiment of thepresent invention, lower resolution patterns (“blocky” patterns) may beused—this can potentially simplify the illumination light engine design.In one exemplary embodiment, 36 patterns are captured with a cameraframe rate of 15 frames/second.

FIG. 4 is an illustration of exemplary post processing that may then beused to mitigate contrast loss due to volume scattering and to recovertarget information. A group of coded images 42 captured by detector 24may be transmitted to computer 30 for post processing. Exemplary postprocessing may then be performed in two separate stages. In a firststage (as shown in FIG. 4 ) the computer 30 applies non-local meanfiltering of the group of coded images 42 to mitigate the backscatter,reduce the undesired noise and improve pattern contrast. In this stage,backscattering component is evaluated jointly using all the coded imagesand reduced from each individual image to provide filtered coded images44. The essence of non-local filter techniques includes matching andgrouping similar blocks in the images for collaborative filtering in atransform domain that the signal is sparse (i.e., the majority ofcoefficients in the transform domain are zeros), as understood by askilled artisan.

In a second stage (as shown in FIG. 4 ), the sequence of filtered codedimages 44 are integrated and image enhancement filtering is performed.In this stage, the computer 30 performs frame integration on thesequence of the coded images 44 to result in integrated frame 46. Thisis followed by image (contrast) enhancement filtering of the integratedframe 46 using a total variation noise reduction filter to result in theenhanced image 48.

The disclosed embodiments may include an exemplary imaging method forimproved imaging of objects underwater. FIG. 5 illustrates a flowchartof such an exemplary method in a degraded underwater visual environment,which commences at Step S500 and proceeds to Step S510.

At Step S510, the apparatus 10 generates spatially varying modulation ona beam of light using a digital micro-mirror device 14. The spatiallyvarying modulation may generate a sequence of coded illuminationpatterns. Operation of the method proceeds to Step S520, where anoptical engine illuminates a target with the beam of light havingspatially varying modulation. Operation of the method proceeds to StepS530. At Step S530, dynamic range detector 24 captures an image of thetarget illuminated with the light having the spatially varyingmodulation.

Operation of the method proceeds to Step S540 for post processing. AtStep S540, the captured image is processed in a first stage, includingapplying non-local mean filtering of the image to mitigate backscatterand reduce undesired noise. Operation proceeds to Step S550 for a secondstage of post processing where the apparatus 10, via the computer 30,performs frame integration on filtered captured images as needed andenhances the integrated image to result in the post processed image.Operation may repeat back to Step S510 for additional imaging asdesired, or stop at Step S560.

The exemplary depicted sequence of executable method steps representsone example of a corresponding sequence of acts for implementing thefunctions described in the steps. The exemplary depicted steps may beexecuted in any reasonable order to carry into effect the objectives ofthe disclosed embodiments. No particular order to the disclosed steps ofthe method is necessarily implied by the depiction in FIG. 5 , and theaccompanying description, except where any particular method step isreasonably considered to be a necessary precondition to execution of anyother method step. Individual method steps may be carried out insequence or in parallel in simultaneous or near simultaneous timing.Additionally, not all of the depicted and described method steps need tobe included in any particular scheme according to disclosure.

FIG. 6A and FIG. 6B depict an exemplary optical engine 12 and anexemplary detector 24, respectively, along with exemplary dimensions.The various components may be housed within watertight cases. Inparticular, FIG. 6A shows light source 16 and SLM engine 50 housedwithin a watertight case 52. FIG. 6B shows a camera 54 and lens 56housed within a watertight case 58. The cases may be compact, with thedetector 24 about the size of a typical twelve fluid ounce beverage can.

FIG. 7 is a table showing cumulative AZ dust, C and beam attenuationlengths for images taken of underwater target 40 at a distance of 4.3meters, where the beam attenuation lengths represent the degradation ofthe water. FIGS. 8-11 show images of underwater target 40 taken with thetarget in increasing levels of water degradation, where images wouldtypically show increasing amounts of backscatter and decreased qualitywith increasing levels of degraded water. As can be seen in FIGS. 9-11 ,image processing under examples of the embodiments improves the qualityof the image in degraded water, with differences more significant withincreased degradation.

FIG. 8 depicts images taken of the underwater target 40 in clear waterand a beam attenuation length of 0.301. In particular, FIG. 8A is animage of underwater target 40 taken with a Thorlabs DCC3626 camera andfloor illumination. FIG. 8B is an image of underwater target 40 takenwith a Nikon camera and flood illumination.

FIG. 9 depicts images taken of the underwater target 40 in degradedwater having a beam attenuation length of 2.855. In particular, FIG. 9Ais an image of underwater target 40 taken with a Thorlabs DCC3626 cameraand floor illumination. FIG. 9B is an image of underwater target 40taken with a Nikon camera and flood illumination. FIG. 9C is a postprocessed image of underwater target 40 taken with a Thorlabs DCC3626camera with coded illumination and post processing via an example of theembodiments. The underwater target can be seen most clearly in FIG. 9C.

FIG. 10 depicts images taken of the underwater target 40 in degradedwater having a beam attenuation length of 4.029. In particular, FIG. 10Ais an image of underwater target 40 taken with a Thorlabs DCC3626 cameraand floor illumination. FIG. 10B is an image of underwater target 40taken with a Nikon camera and flood illumination. FIG. 10C is a postprocessed image of underwater target 40 taken with a Thorlabs DCC3626camera with coded illumination and post processing via an example of theembodiments. The underwater target can be seen most clearly in FIG. 10C.

FIG. 11 depicts images taken of the underwater target 40 in degradedwater having a beam attenuation length of 2.855. In particular, FIG. 11Ais an image of underwater target 40 taken with a Thorlabs DCC3626 cameraand floor illumination. FIG. 11B is an image of underwater target 40taken with a Nikon camera and floodlight illumination. FIG. 11C is apost processed image of underwater target 40 taken with a ThorlabsDCC3626 camera with coded illumination and post processing via anexample of the embodiments. The underwater target can be seen mostclearly in FIG. 11C.

In an exemplary embodiment of the present invention a computer systemmay be included and/or operated within which a set of instructions, forcausing the machine to perform any one or more of the methodologiesdiscussed herein, may be executed. In alternative embodiments, themachine may be connected (e.g., networked) to other machines in a localarea network (LAN), an intranet, an extranet, or the Internet. Themachine may operate in the capacity of a server or a client machine in aclient-server network environment, or as a peer machine in apeer-to-peer (or distributed) network environment. The machine may be apersonal computer (PC), a tablet PC, a set-top box (STB), a personaldigital assistant (PDA), a cellular telephone, a web appliance, aserver, a network router, switch or bridge, or any machine capable ofexecuting a set of instructions (sequential or otherwise) that specifyactions to be taken by that machine. Further, while only a singlemachine is illustrated, the term “machine” shall also be taken toinclude any collection of machines that individually or jointly executea set (or multiple sets) of instructions to perform any one or more ofthe methodologies discussed herein.

The exemplary computer system includes a processing device, a mainmemory (e.g., read-only memory (ROM), flash memory, dynamic randomaccess memory (DRAM) (such as synchronous DRAM (SDRAM) or Rambus DRAM(RDRAM), etc.), a static memory (e.g., flash memory, static randomaccess memory (SRAM), etc.), and a data storage device, whichcommunicate with each other via a bus.

Processing device represents one or more general-purpose processingdevices such as a microprocessor, central processing unit, or the like.More particularly, the processing device may be complex instruction setcomputing (CISC) microprocessor, reduced instruction set computer (RISC)microprocessor, very long instruction word (VLIW) microprocessor, orprocessor implementing other instruction sets, or processorsimplementing a combination of instruction sets. Processing device mayalso be one or more special-purpose processing devices such as anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), a digital signal processor (DSP), network processor,or the like. Processing device is configured to execute listings managerlogic for performing the operations and steps discussed herein.

Computer system may further include a network interface device. Computersystem also may include a video display unit (e.g., a liquid crystaldisplay (LCD) or a cathode ray tube (CRT)), an alphanumeric input device(e.g., a keyboard), a cursor control device (e.g., a mouse), and asignal generation device (e.g., a speaker).

Data storage device may include a machine-readable storage medium (ormore specifically a computer-readable storage medium) having one or moresets of instructions (e.g., reference generation module) embodying anyone or more of the methodologies of functions described herein. Thereference generation module may also reside, completely or at leastpartially, within main memory and/or within processing device duringexecution thereof by computer system; main memory and processing devicealso constituting machine-readable storage media. The referencegeneration module may further be transmitted or received over a networkvia network interface device.

Machine-readable storage medium may also be used to store the devicequeue manager logic persistently. While a non-transitorymachine-readable storage medium is shown in an exemplary embodiment tobe a single medium, the term “machine-readable storage medium” should betaken to include a single medium or multiple media (e.g., a centralizedor distributed database, and/or associated caches and servers) thatstore the one or more sets of instructions. The term “machine-readablestorage medium” shall also be taken to include any medium that iscapable of storing or encoding a set of instruction for execution by themachine and that causes the machine to perform any one or more of themethodologies of the present invention. The term “machine-readablestorage medium” shall accordingly be taken to include, but not belimited to, solid-state memories, and optical and magnetic media.

The components and other features described herein can be implemented asdiscrete hardware components or integrated in the functionality ofhardware components such as ASICs, FPGAs, DSPs or similar devices. Inaddition, these components can be implemented as firmware or functionalcircuitry within hardware devices. Further, these components can beimplemented in any combination of hardware devices and softwarecomponents.

Some portions of the detailed descriptions are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

The instructions may include, for example, computer-executableinstructions and data which cause a general purpose computer, specialpurpose computer, or special purpose processing device to perform acertain function or group of functions. Computer-executable instructionsalso include program modules that are executed by computers instand-alone or network environments. Generally, program modules includeroutines, programs, objects, components, and data structures, and thelike that perform particular tasks or implement particular abstract datatypes. Computer-executable instructions, associated data structures, andprogram modules represent examples of the program code means forexecuting steps of the methods disclosed herein. The particular sequenceof such executable instructions or associated data structures representsexamples of corresponding acts for implementing the functions describedtherein.

In the aforementioned description, numerous details are set forth. Itwill be apparent, however, to one skilled in the art, that thedisclosure may be practiced without these specific details. In someinstances, well-known structures and devices are shown in block diagramform, rather than in detail, in order to avoid obscuring the disclosure.

The disclosure is related to an apparatus for performing the operationsherein. This apparatus may be specially constructed for the requiredpurposes or it may comprise a general purpose computing deviceselectively activated or reconfigured by a computer program storedtherein. Such a computer program may be stored in a non-transitorycomputer readable storage medium, such as, but not limited to, any typeof disk including floppy disks, optical disks, CD-ROMs andmagnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, flashmemory devices including universal serial bus (USB) storage devices(e.g., USB key devices) or any type of media suitable for storingelectronic instructions, each of which may be coupled to a computersystem bus.

Whereas many alterations and modifications of the disclosure will nodoubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that anyparticular implementation shown and described by way of illustration isin no way intended to be considered limiting. Therefore, references todetails of various implementations are not intended to limit the scopeof the claims, which in themselves recite only those features regardedas the disclosure.

What is claimed is:
 1. A method for imaging underwater objects in adegraded underwater visual environment having turbid or turbulent mediumfor close range target inspection, diver assist, and/or roboticoperations, said method comprising: a) generating, via a light sourcecomprising an optical engine configured with a spatial light modulator,spatially varying modulation on a beam of light using the spatial lightmodulator to generate a plurality of coded modulation patterns havingdifferent lighting conditions corresponding to the plurality of codedmodulation patterns to project onto and illuminate a target in thedegraded underwater visual environment at, at least, a CMOS or SCMOScamera associated frame rate, wherein the sequence of coded illuminationpatterns follow a Bernoulli random variable distribution, wherein eachof the different lighting conditions corresponds to one of a sequence ofcoded illumination patterns associated with the plurality of codedmodulation patterns, and wherein the plurality of coded modulationpatterns each has a repeating pre-defined geometric configuration; b)illuminating, via the light source, the target with the beam of lighthaving the spatially varying modulation using the sequence of codedillumination patterns; c) capturing, via a detector comprising a CMOS orSCMOS camera, a plurality of images of said target illuminated with saidbeam of light having said spatially varying modulation through thesequence of coded illumination patterns, wherein the detector isconfigured to capture the plurality of images at the CMOS or SCMOSassociated frame rate; and d) post processing, via the detector or via aremote computing device, the plurality of captured images by applying anon-local means filtering operator configured to jointly operate on allportions of each of the plurality of captured images while groupingsimilar block elements having the repeating pre-defined geometricconfiguration to mitigate backscatter from the degraded underwatervisual environment, wherein the post processing further includes, afterapplying the non-local means filter operator: i) performing frameintegration on the plurality of captured images to generate anintegrated frame, and ii) enhancing the integrated frame by applying atotal variation noise reduction filter to the integrated frame tomitigate backscatter, reduce noise, and/or improve pattern contrast. 2.The method of claim 1, wherein said beam of light is generated using acontinuous wave laser.
 3. The method of claim 1, wherein each of theplurality of captured images includes the target and backscattering andhas data of different patterns of the backscattering in comparison tothe target, wherein the step d) includes removing the backscatteringbased on differences in backscatter between the data of the differentpatterns of the backscattering in comparison to the target.
 4. Themethod of claim 1, wherein at least two of the plurality of imagescorresponding to different ones of the coded illumination patterns andincluding the target and backscattering, the captured plurality ofimages having data of different patterns of the backscattering incomparison to the target.
 5. The method of claim 1, further comprisingreceiving digital modulation pattern data with a controller andmodifying the spatial light modulator to modulate the beam of light inaccordance with the received digital modulation pattern data.
 6. Anon-transitory computer readable medium having instructions storedthereon that, when executed by a processor, cause an underwater imagingdevice to: capture a plurality of images at a CMOS or SCMOS associatedframe rate of a target illuminated with a beam of light having aspatially varying modulation, wherein the target is a close rangeunderwater object in a degraded underwater visual environment havingturbid or turbulent medium, wherein the spatially varying modulation isgenerated via a light source comprising an optical engine configuredwith a spatial light modulator, wherein the spatially varying modulationincludes a plurality of coded modulation patterns having differentlighting conditions that corresponds to the coded modulation patterns,wherein the sequence of coded illumination patterns follow a Bernoullirandom variable distribution, wherein the spatially varying modulationis projected and illuminated on a target in a degraded underwater visualenvironment at, at least, a CMOS or SCMOS associated frame rate, whereinthe each of the different lighting conditions corresponds to one of asequence of coded illumination patterns associated with the plurality ofcoded modulation patterns, and wherein the plurality of coded modulationpatterns each has a repeating pre-defined geometric configuration; andpost process the plurality of images by: i) applying a non-local meansfiltering operator configured to jointly operate on all portions of eachof the plurality of images while grouping similar block elements havingthe repeating pre-defined geometric configuration to mitigatebackscatter from the degraded underwater visual environment, ii) afterapplying the non-local means filter operator, performing frameintegration on the plurality of captured images to generate anintegrated frame, and ii) enhancing the integrated frame by applying atotal variation noise reduction filter to the integrated frame tomitigate backscatter, reduce noise, and/or improve pattern contrast. 7.An apparatus for imaging underwater objects in a degraded underwatervisual environment having turbid or turbulent medium for close rangetarget inspection, diver assist, and/or robotic operations, theapparatus comprising: an analysis system comprising a computer deviceconfigured to evaluate images acquired via a CMOS or SCMOS camera,wherein the CMOS or SCMOS camera captures a plurality of images of anunderwater target illuminated with a modulated beam of light having asequence of coded illumination patterns, with each of the plurality ofimages corresponding to a respective one of a plurality of codedillumination patterns and including the target and backscattering, thecaptured plurality of images having data of different patterns of thebackscattering in comparison to the target, wherein the plurality ofcoded modulation patterns each has a repeating pre-defined geometricconfiguration, wherein the sequence of coded illumination patternsfollow a Bernoulli random variable distribution, and wherein evaluatingthe images comprises processing the plurality of images using anon-local means filtering operator configured to jointly operate on allportions of each of the plurality of captured images while groupingsimilar block elements having the repeating pre-defined geometricconfiguration to mitigate backscatter from the degraded underwatervisual environment, wherein the post processing further includes, afterapplying the non-local means filter operator: i) performing frameintegration on the plurality of captured images to generate anintegrated frame, and ii) enhancing the integrated frame by applying atotal variation noise reduction filter to the integrated frame tomitigate backscatter, reduce noise, and/or improve pattern contrast. 8.The apparatus of claim 7, further comprising a controller configured toreceive digital modulation pattern data and modify the spatial lightmodulator to modulate the beam of light in accordance with the receiveddigital modulation pattern data.